18% grey

[DangerouslyMoody]

Hello! I heard about this in a class a few months back and have been unbal eot find a good description that is easy to understand anywhere...can someone explain this concept to me again please or point me in the right direction where i can get a better concept of this. Thank you!

[Double H]

18% grey reflects (or absorbs) 1/2 of the light that hits it. On the color spectrum, it is 1/2 way between black and white. It gets its name because it is made by mixing 18 parts (18%) solid black paint or pigment to 82 parts solid white paint or pigment. Someone correct me if I'm off base here. RM

[luis_relampago]

White Balance tool basically, what do you whant to know about it? 18% gray is just that a white paper with 18% grey color in it, you can find it in any photo store or shop. It helps you render a white balance on your camera, to get a better representation of the color gamut of your camara profile, basic color calibration for yor DSLR or Camera with custom white balance options.

[bondarnes]

I also use it to tweak exposure. I will read my meter and set that into the camera then shoot a grey card shot to confirm or tweak the meter reading.

[venchka]

Originally, a black & white film concept. Ansel Adams called the middle grey tone (18%) on a negative or print Zone V. He would then meter, expose, develop and print accordingly. Light colored skin is Zone VI. Deep shadows with detail is Zone III. Snow or sand with texture is Zone VII. Zone II and Zone VIII are blocked up shadows or blown out highlights.

In practice, it's a good idea to include both the grey and the white side of the card (buy 2) in a frame for a given lighting situation. Then you can adjust white balance accordingly at the printing stage.

[DangerouslyMoody]

Thanks!! I just remember the speaker talking about shooting something that is solid white and it will turn out not so white because of this grey factor and then he said you want to meter off something that is 18% grey instead...I was just wanting to know a little more about how to do that exactly...do i find something 18% grey,meter off it and then go back to shooting my subject like normal without adjusting my exposure??

[bondarnes]

Originally Posted by dangerouslymoody

Thanks!! I just remember the speaker talking about shooting something that is solid white and it will turn out not so white because of this grey factor and then he said you want to meter off something that is 18% grey instead...I was just wanting to know a little more about how to do that exactly...do i find something 18% grey,meter off it and then go back to shooting my subject like normal without adjusting my exposure??

I am assuming you are shooting in manual exposure mode. After shooting the grey card look at the histogram for that exposure. If the grey card filled the image area you should have one spike. You want that spike to be in the middle of the histogram or as close as possible. If it is to the left you will need to increase your exposure and if it is to the right you need to decrease your exposure. If I can't get it in the center I will select an exposure closest but to the left of center. I hope that helps.

[luis_relampago]

In this case shown on the histogram, the exposure is under by 1/2 stop so when ever you take a picture instead of having the meter in the center you will add that extra 1/2 stop with aperture or shutter speed, so you can have a precise exposure. It could be the other way around, you will have to adjust your meter.

[3n-Out]

Wouldn't the White Balance 18% grey change with available light? That throws a new kink in the knot right?

[kenmyers70]

Originally Posted by luis_relampago

In this case shown on the histogram, the exposure is under by 1/2 stop so when ever you take a picture instead of having the meter in the center you will add that extra 1/2 stop with aperture or shutter speed, so you can have a precise exposure.

Note that in this case there are still significant bright pixels which will get clipped if you increase the exposure in camera. This may be a better time to make sure you shoot raw and adjust the curves in post to avoid blowing out some highlights.

[luis_relampago]

John,
What I think is you would have to be shooting for a long period of time for the ambient light to change, or a storm coming with more clouds and stuff, but in that case you will have to adjust accordingly.

[venchka]

Originally Posted by dangerouslymoody

Thanks!! I just remember the speaker talking about shooting something that is solid white and it will turn out not so white because of this grey factor and then he said you want to meter off something that is 18% grey instead...I was just wanting to know a little more about how to do that exactly...do i find something 18% grey,meter off it and then go back to shooting my subject like normal without adjusting my exposure??

As many have said, buy an 18% grey card and use that until you get the hang of visualizing your exposure values in advance.

White things don't turn out darker because of a grey factor. They turn out darker because the meter wants to make everything look like an 18% grey card. This leads to underexposing light colored objects. That's why you need to overexpose light skin, white clouds, snow, sand, etc. The reverse is true for shadows, black cars, anything dark. The meter will tend to overexpose dark areas. This is why many people use spot meters. A spot meter allows you to selectively meter a scene and adjust exposure to render dark things dark and light things light.

The best evaluative or matrix metering system is located behind your eyes and between your ears.

With all due respect, I doubt that a histogram will show what shadows and snow are going to look like in the final print. But then I don't have a histogram in my brain.

[3n-Out]

Yeah, Since we are talking about white balance I wanted to make sure "I" and anyone else reading this understands that white balance changes depending on "available" light. If you are working in a controlled light enviroment setting your white balance once would be sufficeint. However, if you are shooting outside and take a white balance reading in the shade it can and probably will change if you move to direct sunlight. Therefore, causing major blowouts in photos directly after moving from shade. Correct?

[luis_relampago]

The highlights are critical with digital images, so definitely be careful with your exposures. Raw is a very safe way to shoot, I do both RAW + L jpgs to be on the safe side always.

[3n-Out]

I used to shoot only in JPG but now I shoot only in RAW. The Post side take a little longer but it has saved me on a number of occasions.